Among the elderly, few conditions are more consequential than depression. Rapid evolution in health care systems, new treatment technologies, changing prescription patterns and wider social acceptance of the biomedical basis of depression have created a new context for diagnosis and treatment of depression among the elderly. Such changes make it essential to examine national patterns and trends in the diagnosis and treatment of geriatric depression. In this study, nationally representative data from the Medicare Current Beneficiary Survey, including detailed longitudinal information on use of pharmaceuticals and mental health services, will be used to examine patterns of diagnosis of geriatric depression; analyze trends in and predictors of antidepressant treatment among the elderly; analyze use of specialty mental health services among elderly diagnosed with depression; investigate the extent and predictors of early discontinuation of antidepressant use; model amounts received and duration of mental health services use; and compare observed treatment patterns to those recommended by treatment guidelines. Variations in these patterns by care sector (mental health specialty versus general medical care), payer system (managed care versus fee-for-service), sociodemographic subgroup, insurance coverage, medical comorbidities, and other factors will be evaluated. We will also use data from the National Ambulatory Medical Care Survey, which link physician specialty, assigned diagnoses and medications prescribed during physician visits, to explore the evolving roles of the specialty and general medical care sectors in treatment of geriatric depression, and analyze the relationship between diagnoses assigned and psychotropic treatments prescribed at medical visits. Data from both sources will also be used to study the diffusion of selective serotonin reuptake inhibitors (SSRIs) among the elderly. These analyses will contribute to a better understanding of the process of diagnosis and treatment of depression in the elderly population, so that barriers to optimal care can be identified and addressed. They will also provide important information on trends in treatment patterns and shed light on the impact of health care system changes on the treatment of depression.